In a pan add oil and once the oil is hot,reduce flame,add cumin seeds,coriander seeds,urad dal,chana dal and red chillies and saute till the dal turns light brown.

Add the roughly chopped onions , garlic' s, red bell pepper and salt mix well,saute for 9 - 10 mts in a medium flame.Add coriander leaves saute for 2 minutes.Turn off heat and cool.
Add this mixture in to a blender and tamarind .Grind it in a mixer into smooth paste .
Remove into a serving bowl.
Heat a tsp of oil in a small pan,add the mustard seeds and allow them to splutter.Add the curry leaves,red chilies and asafoetida and turn off heat.
Pour this tempering over the chutney and Serve with idli or dosa.